1. Field of Invention
This invention relates generally to adhesive compositions and more particularly to adhesive compositions based on vinyl ester polymer dispersions.
2. Description of Prior Art
Aqueous dispersions containing vinyl ester polymers, for example, vinyl acetate polymers or copolymers, are well known and have found particular utility in adhesive applications. For such uses it has been customary to polymerize or copolymerize vinyl acetate in an aqueous medium containing polymerization initiators and water-soluble protective colloids. Many of the problems associated with the preparation of useful dispersions have been discussed in a variety of patents, among which the following are included: U.S. Pat. No. 2,227,163 issued to Werner Starik and Heinrich Freudenberger on Dec. 31, 1940; U.S. Pat. No. 2,398,344 issued to Henry M. Collins and Mogens Kiar on Apr. 16, 1946; U.S. Pat. No. 2,388,600 issued to H. M. Collins on Nov. 6, 1945; U.S. Pat. No. 2,892,802 issued to Eugene P. Budewitz on June 30, 1959; U.S. Pat. No. 2,956,962 issued to Samuel P. Wise on Oct. 18, 1960; U.S. Pat. No. 3,094,500 issued to Stedman C. Herman on June 18, 1963, and Canadian Pat. No. 812,285.
One such problem in providing a suitable adhesive based on a vinyl acetate polymer has been improving the viscosity stability and coagulation resistance of the adhesive dispersion while maintaining improved water resistance of the adhesive after it has been deposited from the dispersion. Viscosity stability and coagulation resistance of the adhesive dispersion should be maintained both during and after preparation and should not be materially affected by either aging at elevated temperatures or freezing.